Washington: An international team of scientists has found the first "super Earths" to be discovered around two Sun-like stars.
These are rocky planets larger than the Earth, but smaller than ice giants such as Uranus and Neptune.
Unlike previously discovered stars with super-Earths, both of the stars are similar to the Sun, suggesting to scientists that low-mass planets may be common around nearby stars.
"Over the last 12 years or so nearly 400 planets have been found, and the vast majority of them have been very large - Jupiter mass or even larger," said researcher Paul Butler of the Carnegie Institution`s Department of Terrestrial Magnetism.
"These latest planets are part of a new trend of finding much smaller planets - planets that are more comparable to Earth," he added.
The international team of researchers, co-led by Butler and Steven Vogt of the University of California, Santa Cruz, was able to detect the new planetary systems by combining data from observations spanning several years at the W. M. Keck Observatory in Hawaii and the Anglo-Australian Telescope in New South Wales, Australia.
The researchers used the subtle "wobbling" of the stars caused by the planets` gravitational pull to determine the planets` size and orbits.
In this study, the researchers found evidence of three low-mass planets, the smallest of which is five times the mass of Earth and speeds around the star once every four days.
Butler points out that the signal produced by this planet was one of the smallest ever detected.
"One has to be very cautious when you claim a discovery," he said. "What gives us confidence is that we see the signal from two separate telescopes, and the two signals match up perfectly," he added.